continental shelf

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A submerged border of a continent that slopes gradually and extends to a point of steeper descent to the ocean bottom.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun nautical The area of sea around a land mass where the depth gradually increases before it plunges into the ocean deeps

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the relatively shallow (up to 200 meters) seabed surrounding a continent